In recent trend, in order to support diverse service requirement for 5G, network slicing is a must solution. The following definition of network slice had reached an agreement: “A Network slice is an end-to-end (E2E) concept including core network (CN) slice parts and radio access network (RAN) slice parts. The RAN part of the slice routes signalling to the CN part of the Slice.” Regarding the network slicing scenario, there was an interim agreement: “A user equipment (UE) may access multiple slices simultaneously via a single RAN.” Regarding the RAN slice parts, a definition was proposed: “The combination of L1 resource component and L2 configuration/functions, to address the needs of different services and requirements, can be defined as RAN Slice.”
Long term evolution (LTE) (i.e. 4G) is a homogeneous network, and each node is assumed with the same capability. 5G, however, is assumed as a multi-tier network, which means each node is with different (or limited) RAN-slice capability. Therefore, a problem that additional handover caused by potential services in multiple-slices scenario may arise.